Various extension-related cleanup and simplifications.

src/extensions/externalize-string-extension.h

Index: src/extensions/externalize-string-extension.h
diff --git a/src/extensions/externalize-string-extension.h b/src/extensions/externalize-string-extension.h
index 3d1e438f7f2617b806ccf25ee96f4b6eb0729284..d0cb5e47d3d82a5ee942d3037a8d6c73ce9626c1 100644
--- a/src/extensions/externalize-string-extension.h
+++ b/src/extensions/externalize-string-extension.h
@@ -41,7 +41,7 @@ class ExternalizeStringExtension : public v8::Extension {
       v8::Handle<v8::String> name);
   static void Externalize(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void IsAscii(const v8::FunctionCallbackInfo<v8::Value>& args);
-  static void Register();
+
  private:
   static const char* const kSource;
 };